Energy balance, exercise-induced muscle damage, and the efficacy of nutritional interventions on recovery in female dancers

It is well-documented that strenuous physical activity has the potential to elicit exercise-induced muscle damage (EIMD), particularly when the exercise is novel and has an eccentric component. Given that the symptoms of EIMD can compromise subsequent performance, there has been substantial investigation into potential strategies that might reduce these detrimental effects in athletic populations. However, while significant advances have been made in this field, few investigations address the diversity of exercising populations who might experience EIMD following the activities they engage in, and the strategies that could facilitate their recovery. Globally, dance and dance-based exercise are popular forms of recreational physical activity, and the intensity and volume of exercise previously reported in highly trained and professional dancers can often be comparable to that of many other elite athletes. The overall purpose of this thesis was to understand the nutritional challenges facing female dancers, increase knowledge of the EIMD response, and examine potential nutritional interventions to reduce the negative issues associated with damaging exercise in this understudied population. The first study characterised the typical energy intake (estimated by combined 24 h recall and weighed food diary) and energy expenditure (estimated by the sum of basal metabolic rate, the thermic effect of food, and physical activity energy expenditure) of pre-professional contemporary dancers during 7 days of full-time training. This study determined that there is a prevalence of energy deficiency in this population (with an average daily deficit of -356 ± 668 kcal or -1.5 ± 2.8 MJ). Additionally, the second study demonstrated that female dancers experience EIMD, both from dance-specific and repeated-sprint exercise; with observed increases in muscle soreness, limb girth, plasma creatine kinase, and reductions in muscle function (all p < 0.05). These data served to inform the final two experimental chapters, which sought to investigate the role of nutritional interventions in alleviating the various symptoms of damage following repeated-sprint exercise in female dancers. Montmorency tart cherry supplementation accelerated recovery of countermovement jump height compared to placebo (p = 0.016). There was an improved recovery of reactive strength index (p = 0.016), flexibility (p = 0.050) and reduced CK (p = 0.002) following supplementation with whey protein hydrolysate. Consequently, this research provides justification for the use of these supplements as practical interventions, which could be implemented to benefit the day-to-day life of a dancer; not least for promoting recovery, but also contributing to maintaining energy balance